The present invention relates to a digital oscilloscope and method of operation, and particularly to such an oscilloscope and method of operating the same which pemits the user to differentiate between original sampled data and interpolated information.
A conventional digital storage oscilloscope samples an input waveform at a large number of sample points, converts the analog sample information to digital form, and stores the resulting digital information in computer memory. The digital information is repeatedly retrieved and re-converted to analog form for presentation on the screen of a cathode-ray-tube.
The digitized samples of the input waveform represent discrete points on the waveform and in order to avoid presentation of a discontinuous trace consisting only of these points, some kind of interpolation mechanism is frequently employed to provide an interpolated trace between the original points. A suitable interpolator comprises a sine interpolator, or one having a sin x/x characteristic adapted to provide a smooth or sine-wave-like trace between the original data points. However, the same interpolator that correctly portrays sine wave information from memory also introduces what appears like pre-shooting and over-shooting on pulse information or information having rapid rise and fall times. Over-shoot and ringing can obscure the true waveform.
As one possible solution, a digital storage oscilloscope can be provided with more than one interpolator, for example one interpolator for sine wave information and another with good pulse response but lacking in ability to interpolate sine waves. The user of the oscilloscope must choose between the two different waveform displays for the same acquired data sequence, and neither display may be entirely accurate.